Recently, there has been widespread use in homes of PCs (Personal Computers) and digital home appliances such as hard disk recorders for recording, into recording media such as HDDs (Hard Disk Drives) and BDs (Blu-ray Discs), programs broadcast via a terrestrial wave, BS (Broadcast Satellite), CS (Communication Satellite), and so on. With the development of the communication network technology and communication devices, many of these devices have a function of connecting to a communication network. This increases the spread of an environment that easily realizes remote content playback, content copy, and content move among devices in homes via the communication network. Here, the remote content playback indicates that a content recorded in a recording device is played back by a playback device that is connected to the recording device via a communication network in home.
In the case where a content is transmitted between devices in home, a predetermined protocol is used by a transmission device and a reception device.
The “content” here is, for example, data in MPEG (Moving Picture Experts Group) 2-TS (Transport Stream) format. This data contains an ES (Elementary Stream) of each of video and audio and information accompanying a content such as PSI (Program Specific Information) which have been multiplexed.
As a protocol specification for sharing a content between devices in such a home area network, the DLNA (Digital Living Network Alliance) guidelines are known, for example.
The DLNA guidelines include standards which have been selected among conventional standards and specified, in order to achieve a high interconnectivity in the home area network. The DLNA guidelines specify that, as long as packet communication can be performed via TCP/IP (Transmission Control Protocol/InternetProtocol, any method of connecting between devices may be employed regardless of whether a communication is a wired communication or a wireless communication. For example, the DLNA guidelines specify, as the wired communication and the wireless communication, connection via a wired LAN such as IEEE802.3 and a connection via a wireless LAN such as IEEE802.11a/b/g in which packet communication can be performed via TCP/IP, respectively. Furthermore, the DLNA guidelines specify UPnP (Universal Plug and Play) for definition of device discovery and control method on the home area network, and definition of search, selection, management method of a content.
Also, in order to transmit a program broadcast via a terrestrial wave, BS, CS, or the like via a protocol specified by the DLNA, there needs an art for copyright protection. As an art for protecting a path for transmitting a content that is a target of copyright protection, DTCP-IP (Digital Transmission Content Protection over Internet Protocol) has been standardized. Furthermore, in the case where a copyright of a content needs to be protected, video output needs to be performed based on copyright protection information set for each video stream section of the content in order to appropriately reflect an intention of an owner of the copyright.
Furthermore, the Dubbing 10 system permits multiple times of copies of a content to another device.
With the widespread of devices capable of dealing with contents in homes, the following usage is presumed where a user adds a content created by the user to an original content, which has been moved from a first device to a second device, or modifies the original content to create an edited content, and then moves the edited content back to the first device as the original content. Here, assume that the edited content is created by adding an advertisement content, modifying the original content into a parody content, or the like. If the edited content is distributed, especially if the edited content is distributed as the original content, rights relating to the original content of an author, a creator, and so on might be infringed. This is a problem.
Accordingly, in such a case, it is necessary to clearly distinguish between the edited content and the original content.
According to a conventional content management method, the UPnP specified by the DLNA guidelines is used for searching for a plurality of contents on a server to obtain a content list, and distinguishing between the contents based on IDs of the contents contained in the content list. However, this method is incomplete to judge whether the contents are the same content. For example, in the case where the contents are the same content but each have a different ID, the contents cannot be considered as the same content. On the contrary, there is a case where the contents have the same ID but are each a different content. Accordingly, it is difficult to judge the sameness of content only based on information of the content list obtained via the UPnP.
In order to solve this problem, Patent Literature 1 discloses a content reception device that performs comparison processing on all the pieces of stream data of an original content recorded on a server and all the pieces of stream data of a received content, thereby to judge whether the original content and the received content are the same.